1. Field of the Invention
The present invention relates to mirror assemblies in a laser scanning machine, and, more particularly, to mirror assemblies for optical path reversal in an electrophotographic machine.
2. Description of the Related Art
In order to provide a color electrophotographic printer with a same printing speed as a monochrome electrophotographic printer, it is known to substantially simultaneously produce the images on each respective electrophotographic drum for each of the colors of the printer. This is known as "tandem color laser electrophotographic architecture" and requires four laser print image lines to be respectively generated by cyan, magenta, yellow and black printheads, all of which must be packaged in a reasonably sized machine housing.
In order to minimize the size of a tandem color laser printer system, a compact laser printhead is required. Meeting this compactness objective requires folding the optical path back over top (or under) the mirror motor. To accomplish this, a 180.degree. reversal of the optical path is achieved by a set of mirrors mounted as a pair, which are oriented at an angle of approximately 90.degree. relative to each other. This 90.degree. mirror set is located between the scanning polygon mirror and the first f-theta lens. In order to avoid undesirable bow and spot distortions occurring at the image plane, it is critical that the scanned laser beam pass through the desired optical axis of each lens. Thus, extreme care must be taken to physically align the source of the laser beam and/or the lens such that the scanned laser beam passes through the desired optical axis of the lens. Further, the laser beam and/or the lens must be provided with a shiftable mounting in order to perform such alignment.
What is needed in the art is a method of reversing a laser beam between a scanning mirror and a lens in an electrophotographic machine Such that a physical alignment procedure does not need to be performed on the source of the laser beam and/or the lens.